1. Field of the Invention
The invention relates to the field of microwave ovens and more particularly to quartz lamp infrared heaters included therein.
2. Brief Description of the Prior Art
Quartz infrared lamp have been included in microwave ovens for the purpose of broiling or browning, see e.g., U.S. Pat. Nos. 4,096,369 filed Nov. 15, 1976 to Tanaka et al. (assigned to Matsushita Electric Industrial Co., Ltd. of Japan) and 3,878,350 filed July 14, 1972 to Takagi (assigned to Sharp Kabushiki Kaisha of Japan).
It has been the practice to enclose them in a wire mesh to shield them from microwaves. See the above-referenced '369 and '350 patents. The resulting structures not only occupy valuable oven space, but are also not easily removable or cleanable. In addition, the wire mesh masks a good deal of the infrared, thereby restricting the efficiency of the lamp and unnecessarily heating the microwave shield up to a high temperature.
The quartz infrared lamp structure of the present invention not only has no microwave shield, which leads to a much higher infrared efficiency, but it is also removable both for easy cleaning and for providing a larger oven cavity for microwave-only operation.
The power leads to the quartz lamps potentially conduct a large amount of microwave energy out of the cavity. To prevent the escape of microwaves along the power leads, a quarter-wave choke has conventionally been employed external to the oven cavity, albeit, not heretofore with quartz lamps. See e.g., U.S. Pat. Nos. 4,298,780 filed Mar. 12, 1980 to Suzuki and 4,149,056 filed May 5, 1977 to Kaneshiro et al. (assigned to Sharp Kabushiki Kaisha of Japan). It is a common feature of these chokes that they are not designed to be operable during microwave heating with the infrared heating element removed. In contrast, the choke design of the present invention allows removal of the infrared heater for cleaning as well as during microwave operation.